This invention relates to a process for the production of a metallic article having a matt nacreous appearance in which the metallic substrate is a white-silvery metal such as zinc, aluminum, magnesium, iron or an alloy thereof and also relates to the metallic article produced thereby.
Heretofore, conventional metallic articles having a matt nacreous appearance were produced by a satin nickel and chromium plating process (for example, a satin nickel plating process by Udylite Corp.) comprising preparing a nickel plating bath in which are suspended non-conductive fine particules such as barium salt particles and then simultaneously electrodepositing the nickel and barium salt particles, or by a process using a synthetic resin coating material prepared by kneading aluminum fine particles therewith. Such conventional metallic articles which are metallized products are widely used for the purpose of decorating automobile and architectural hardware and daily necessaries as well as of anti-glaring effect.
However, the aforesaid satin plating process requires, as a matter of course, a plating apparatus including a power source and is disadvantageous in that sewage from the apparatus must be treated under the strict regulations for prevention of environmental pollution and, further, there are many limitations on the sewage treatment. In addition, when said process is attempted to be used in plating on a zinc-based alloy, it requires three steps of copper plating, nickel plating and chromium plating thereby rendering the process operationally complicated with an attendant high operational cost.
On the other hand, the metallic paint coating process is operationally simple; however, the metallic coatings obtained thereby appear less transparent and have less decorative effects than those obtained by the satin nickel plating process since they relay for their matt nacreous appearance on the aluminum powder contained in the coating formed thereon and, further, they are very often unsatisfactory in corrosion resistance and adhesion of the coating to the substrate whereby they tend to be remarkably degraded in appearance. In addition, an electrostatic coating process usable for mass production of coated products is difficult to apply to said metallic coating since the aluminum powder contained in the layer formed by the said coating is electrically conductive.
Various studies were made by the present inventors in attempts to find a new process for the economical production of excellent anti-corrosive metallic articles in which a clear paint coating is securely bonded to the metal substrate, with the result that there was developed such a new process which was advantageous over the conventional processes. This invention is based on this finding or discovery. According to this invention, there may be obtained metallic articles having a high-class decorative matt nacreous appearance which is apparently more attractive than metallic coated articles. In addition, such metallic articles are more excellent in corrosion resistance than satin nickel plated articles and are also excellent in adhesion of coating with elimination of conventional unsatisfactory adhesion thereof.